Cyclohexene production



Oct. 25, 1949. H. H. voGE ETAL CYCLOHEXENE PRODUCTION Filed Sept. 29, 1947 Myer/fors:

Patented Oct. 25, 1949 UNITED STATES PAT ENT CYCLOHEXlTODUCTION Hervey H. Voge, Berkeley, andl George ML Good,

Albany, Calif.,v assignors to Shell' Development Company, San:y Francisco, Calif., a' corporation of Delaware Application September 29, 11947, Serial No. 776,764

10 Claims (Cl. 260666) Thisinvention relates to the production: of` cyclohexane. The inventionl relates more particularl'y toa process for the production of cyclo.- hexene of high purity from` olefinic hydrocarbon mixtures comprising methylcyclopentane in adimixturewith close boiling hydrocarbonsv inseparable therefrom` on' a practical scale by fractionat'i'ng means.

Cyclohexene is of' value as the starting material for thel productionv of a Wide Variety of valuable organic chemical derivatives which are themselves often impor-tant as intermediates in the manufacture ofy highly desirableI products, such as, for example, the polyamide resins. Methods have been disclosed for the production of-cyclo'hexene by-processes comprising the vintermediate production of a compound from which the desiredl cyclohexene could be produced with practical yields by available processes. Such processes are, however, not onlycumbersome, but are generally'relatively costly because of the nature` ofthe individualA chemical processing steps involved. A process enabling they efficient production of= cyclohexene from readily available hydrocarbons is therefore particularly desirable. Processes, such as theA process of U. S.- Patent 223 85,1555, bring Within the -realm of l practica-bility theprod'uction ofl cyclohexene from cyclohexane. Such'methods as disclosed heretofore, however, doI not lend themselves to thev practical scale production ofv cyclohexeneof high purity from the unsaturated 'six'carbon atom -cyclic hydrocarbons, suchas; for example, the methylcyclopentenes' or methylcyclopentane, present in substantial amounts inreadily availableV but highlycomplex hydrocarbon mixtures. Such` readily available olenic hydrocarbon mixtures compriseK those obtained' as products in the thermal or catalytic treatmentof naturally occurring or synthetcally produced-hydrocarbons; Thus, the hydrocarbon mixtures boiling, in the motor fuel boiling range obtained', for' example, by the catalytic cracking OFhydrOcarb'ons, generally containv a substantial amount of I methylcyclopentane and methylcy'clopentenes. The complexity of these hydro-carbon mixtures andthevv presence therein of amultiplicity of hydrocarbons boiling at temperatures in close-proximity to the boiling temperaturesof met-hylcyclopentane or the methylcyclopentenes renden extremely dicult andy oftenimpossibl'e tlie' separation therefromof these' cyclic hydro'- carbons-'suiciently 'free of close-boiling yaliphatic hydrocarbons by methods available heretofore to errableetheirl conversion \to cyclohexenef of relatively-"high purity.- The complexityv of operative steps' required', andi-r1'- somer cases the rie'ed for the usev of catalys'tsoi reagents! of relatively high cost, to produce m'etl'iy'lcyclop'elit'ahe'l or Iiiethyllcyclopentene of silllehtdegree of purity' for' elil cient conversion tofcyclohexne-'by methods avail'- able heretofore often`v rf'enderv these' processes highly impractical.- 'Ih'eldiliiculty of separating methylcyclopentane or a single oneio'flth methyl'- cyclopenteneisomeriiiirelatively pure State from such' hydrocarbon mixtures Aby? methods available heretofore' is rendered apparent arealiza-tion of the nuiltipli'cityl'of hydrocarbons havingclosely approximating boilingterr'ip'eratiires generally presentfv tlfier'ein.l a hydrocarbon fraction consisting 'essentially @hydrocarbons 'having six carbon atoms tothe-moleculearid havngfa boiliing'range of 65?02 126696' C5, separated from'an ol'enic crack-edf gasoline byl fractionation Will generally' contain"- 'metl'iylcyclopentene" ad'- mixtur'e' with the closely boiling'hydro'carbons iii-- dicated inf thef'llowing'- tabl-e:

bons boiling in the range of from 72 C. to 85 C. encountered in olefinic cracked gasolines:

Table C' 4,4-dimethy1pentene-1 '72 4,4-dimethylpentene-2 76 3,3-dimethylpentene-1 77 2,3,3-trimethy1butene-1 78 2,2-dmethylpentane 79 2,4-dimethylpentane 81 2,4-dimethylpentene-1 81 3,4-dimethylpentene-1 81 2,2,3-trimethylbutane 81 2,4-dimethylpentene-2 82 3methylhexene1 84 2,3-dimethylpentene-1 85 B-ethylpentene-l 85 4-methylhexene-2 (trans) 85 The relatively wide spread in boiling range of the three methylcyclopentene isomers and the fact that .the practicality of a process for the production of relatively pure methylcyclopentenes is often dependent upon a recovery of at least the greater part of all three, render the use of processes involving such steps as fractionation and olefin extraction, as utilized heretofore, highly unsatisfactory.

In copending applications Serial No. 776,763,

filed September 29, 1947, and Serial No. 776,765,

led September 29, 1947, pr-ocesses are `disclosed and claimed enabling the eiicient production of methylcyclopentenes and cycl-ohexene in a high state of purity from the methylcyclopentene content of the complex hydrocarbon mixtures comprising them in admixture with close boiling open chain aliphatic hydrocarbons. The methylcyclopen-tane content of the charge, which generally constitutes an additional valuable source of unsaturated cyclic hydrocarbons is, however, not recovered as such, or as methylcyclopentene or cyclohexene free of close boiling open chain aliphatics, by these methods. Separation of a methylcyclopentane-containing fraction -fr-om such complex hydrocarbon mixtures .and subjecting it directly to such a step as dehydrogen-ation will obviously result in the `production of an unsaturated hydrocarbon mixture, the complexity of which often renders difficult, if not impossible, the eicient production of cyclohexene of high purity therefrom .by methods available heretofore. Separation of the olefinic 4content of the methylcyclopentane fraction prior to the dehydrogenation step does not provide the solution to the problem since the resulting dehydrogenate, as :a result of dehydrogenation of both cyclic and open chain saturates will again consist of a complex mixture of both cyclic and straight chain unsaturates of close boiling temperatures inseparable on a practical scale by fractionation.

It is an object of the present invention to provide an improved process for the more efficient production of cyclohexene from readily available complex methylcyclopentane-containing hydrocarbon mixtures comprising methylcyclopentane in admixture with close boiling aliphatic hydrocarbons inseparable therefrom on :a practical scale by ordinary fractionating means.

Another object of the invention is the lprovision of :an improved process -for the more eincient production of cyclohexen-e of high purity from cracked olefinic gasolines.

Another object of the invention is the provision of an improved process for the more emcient Iproduction of cyclohexene of high ypurity 4 from olenlc hydrocarbon fractions comprising methylcyclopentane in admixture with close boiling aliphatic hydrocarbons. Other objects and advantages of the present invention will become apparent from ithe following detailed description thereof.

The -objects and advantages of the present invention are obtained by fractonating a complex hydrocarbon mixture comprising methylcyclopentane in admixture Wi-th close boiling open chain aliphatic hydrocarbons -from any suitable source, such as, for example, a cracked gasoline, to separate therefrom a methylcyclopentane-containing fraction. The methylcyclopentan-e fraction comprising the methylcyclopentane in admixture with close boiling open chain Ialiphatic hydrocarbons is subjected to catalytic hydrocarbon dehydrogenating conditions effecting the conversion of methylcyclopentane to methylcyclopentenes and the simultaneous conversion of at least a substantial part of the open chain saturated aliphatics present to open chain olefinic hydrocarbons. The Iproducts of dehydrogenation are -fractionated to separate :therefrom a lower boiling hydrocarbon fraction comprising S-methylcyclopentene in admixture with close boiling aliphatic hydrocarbons having six carbon atoms to the molecule, anda higher boiling hydrocarbon fraction comprising l-methylcyclopentene and 4- methylcyclopentene in admixture with close boiling aliphatic hydrocarbons having seven carbon atoms to the molecule. The lower boiling hydrocarbon fraction is subjected to olefin isomerizing conditions effecting the conversion of 3-methylcyclopentene to cyclic olens comprising 1- methylcyclopentene and Ll-methylcyclopentene in a rst isomerizing zone. 'Ihe higher boiling hydrocarbon fraction is separately subjected to olefin isomerizing conditions effecting the conversion of 1-methylcyclopentene and 4-methylcyclopentene to cyclic olens comprising 3- methylcyclopentene in -a second isomerizing zone. Methylcyclopentenes consisting essentially of 1- and 4methylcyclopentenes are separated in a high state of purity from the eiiiuence of the first isomerizing zone. Methylcyclopentenes consisting essentially of 3methylcyclopentene in a high stat-e of purity are separated from the eiiluence of the second isomerizing zone. 'I'he methylcyclopentenes thus separated from the eilluence of the first and second isomerizing zones are combined and subjected to olefin isomerizing Vconditions in a third isomerizing zone effecting the conversion of methylcyclopentene to cyclohexene. Cyclohexene in a high state of purity is sepaarted as a final prod-uct from the efiluence of the third reaction Zone.

The process `of the invention is applied to the production of cyclohexene from complex hydrocarbon mixtures, comprising methylcyclopentane in admixture with close boiling aliphatic hydrocarbons, obtained from any suitable source. Thus, the charge to the system may comprise the methylcyclopentane containing hydrocarbon mixtures obtained in the thermal or catalytic treatment of hydrocarbons, such as, for example, the methyl-cyclopentane-containing hydrocarbon mixtures obtained in the thermal and catalytic cracking, hydrogenation, destructive hydrogenation, isomerization, reforming, alkylation, and the like, of hydrocarbons. Other lsuitable starting materials comprise the products of hydrocarbon synthesis, the methylcyclopentane-containing hydrocarbon mixtures of natural occurrence, etc.

In order to set forth more fully the nature oi arcanes tnelinvention, it will be described herein with rer- 'bin'ce #to tli iatlilcheddrawihg'wherein Ithe Single glfl'e represents l. 'i-lbl `'0I' -ISS diagrammatic@ elevational 'view of one ofaiparatus suitable for executing the process of the invention.

`Rferring to rthe drawing, 'a complex hydrocarbon mixture comprising inethylcyclopentane in "aidmixture 'with l'close boiling lopen chain aliphat- -hydrocarbons, las. .ror example, a cracked gasoline, taken ifr'om an ol'itsidesource, is forced th'rough yline "Il) into a feed lfifactionating zone. Yin the drawing the "feed ltractionating Zone is represented by 'the vsingle fractionator I`I. It Wiil rbe understood that in .practical application "'of the 'invention fa plurality .of fractionators will generally be employed. In 'feed fractionator I-I, the gasoline iis .fractionated to separate therefrom :a hydrocarbon -fraction Icomprising methyl- -icyclp'ehltane 'admixture with close boiling Vroper-i chain aliphatic hydrocarbons having six @sind fs'even carbon atoms 'to the molecule. Thus, the m'ethylcyclopentane-containing fraction may 4:have a boiling range of, for example, 'from about L68 Cfto about"74 C. A fraction having a somewhat broader boiling range `may `be employed lthe "scope `'o'f the invention.

The methylcyelopentane#containing fraction is 'passed from 'feed fractionator vI I through vali/ed `:line M into a sui-table heating zone, such las, fore'xa'mple, an -externally Vheated coil I5 pofsition'ed lin 'a `furnace structure I6. From coil I5 the heated lmethylcyclopentane-containing hydrocarbons are'passed through-line I1 into a dehydrogenatio'n zone. The fdehydrogenation zone may comprise a 'reaction chamber I8. Within `inaction 'chamber .'I8 the methylcyclopentane- Arc'"ontaining 'fraction is 'contacted 'with a suitable hdehyd'rogenation catalyst, `for example, a catalysto'f the chrome-alumina type, 'such as a catalyst consisting essentially of an intimate mixture L -of oxides fof chromium land aluminum, under hydrocarbon dhydrogenating -conditions effecting the conversion of methylcyclopentane to methylcyelopentenes. The temperature within lrea'ctor- I8 'is maintained :above about 500 C., for example, 'in 'the range of `lfrom about 450 C. to labout'ob" C.,and preferably from about 500 `C. v"to #about "600 C. Temperature `conditions within reaction chamber `I8 are maintained by the ne'at Yirii'nut irl-to `the methylcyclopentane fraction flowing lthrough -c'oil i5. The -dehydrogenation reaction -iis 'effec-ted yfat 4atmospheric lor superat- YLrn'osphe'i'ic `pressures in the range of, for example, from about 1 to about 50 pounds absolute, fand 'preferablyfrom about .10 to about 20 pounds absolute. :Higher vpressures may, however, be 1e'n'iplo'yed. "Contact times in the range -of from "about 0&2 second to about l5 seconds have been found suitable with @a :liquid hourly space velocity o'f from about 0.5 to 10. Although a chro- 'In'li-ii'rn loxide-'aluminum Yoxide `catalyst is chosen 'iin the f-il-lustrative description of the invention as '-the idehydrogenation "catalyst l'employed in reaction-chamber I8., thc invention is in no wise limited to the use of this particular catalyst. .Other suitable ldel'ly'drogenation catalysts comprise, yfor "example, oxides of metals of groups V and VI` -of the periodic table. These materials are preferably employed in combination with suitable :solid Kdispersing agents such as oxides of metals of lgroups II, III and IV of "the Aperiodic table, .particular-ly oxides of aluminum, 'magnesium, zirconium; bauxite, clays, such "a's bentonites, lmontmorilloniten etc.'; ki'eSeIguhr; crushed silica; glauconitesand'; ete. Another suitable catalyst is activated carbon, alone or promoted with oxides of 'metals Vof "groups "V and Under 'verted -:to methylcyclopentenes essentially consisting of l-methylcyclopentene, A3-methylcyclolpentene and 'li-methylcyclopent'ene Ywithin reaction chamber 118. Smaller lamounts of methyllcyclopen'tadiene and aromatics will also form. The'open chain aliphatic hydrocarbons originally present in the methylcyclop'entane fraction, such ias the h'exanes and-some heptanes, will be 'oonverted, iin part, "to open chai-n 'olefl'nic hydrocarbons and aromatics. The following `example is 'illustrative of the fdehydro'genation vof 'a .methylcyolopentane-contain-ing vfraction -in accordance with the 'process of the invention:

Example I A methyl'cyclopentane concentrate separated by fractionation from a petroleum fraction is de- 4hydrogenated by contact with 'a catalyst consisting V'of chromia-alumina containing 13.7% Cr, at a temperature of 550 C., atmospheric pressure fand a liquid hourly space velocity 'of 2. A conversion of 23% is obtained. The converted `material contains 36,91% mixed methylcyclopenltenes. In a repetition of the operation under -4substantially identical conditions, but with the 'exception that hydrogen is added to the feed :in a 1 to -1 mole ratio, the conversion `of methylcyclopentane is 26% and lthe `converted material contains '45.6% methylcyclop'entenes.

The eiiuence emanating from reaction cham- -ber 18, ldue to the presence vof "c1-ose boiling aliphatics Yoriginally .present in the charge or formed during the dehydrogenation, will gener- -ally be of su'ch complexity as `to vrender exceedingly difficult, if not impossible, the separation therefrom of metlylcyclopentenes free from -open chain aliphatic hydrocarbons. by such steps as fractionation las conducted on a practical scale. The complexity of the resulting mixture will furthermore render impractical the obtaining of cyclohexene of high purity therefrom by methods available heretofore. In accordance with the invention the eliiuence from reaction chamber I8 is therefore passed through line 20 `provided with suitable Vcooling means, such as, for example, a 4heat exchanger 2I, into a .suitable dehyolrogena'tion product separating zone.

In the drawing the dehydrogenation product separating Zone is depicted by fractionators 22, 23 and 24. Within Vfractionator 22 a vapor fraction comprising hydrocarbons boiling below about 65 C. is separated as a vapor fraction from a liquid 'fraction comprising hydrocarbons boiling above about 65 C. The liquid fraction comlprising isomeric `methylcyclopentenes in admixvture with close boiling Ialiphatic :hydrocarbons and unconverted methylcyclopentane is passed Afrom fractionator 22 by means of line `2b into -fractionator-ZS. Within fractionator 23 a vapor fraction comprising 3-methylcyclopentene in radlmixture with close boiling hydrocarbons, such as, for example, a fraction boiling in the range -of from about 66 C. to about '68 C., is sepa'- rated as a vapor fraction from a liquid fraction comprising higher boiling hydrocarbons. The Vapor fraction comprising 3-methylcyclopentene is taken overhead from fractionator 23 through .line 28 and forms the charge -to a rst isomeri"- ying Zone.

The liquid fraction ispassed from fractionator 2-3 through line 29 into fractionator 24. Within fraction-ator i215 "a vapor fraction ycomprising unco'nverted methyloycl'opentane, such =as, forexample, Qa vfraction boi-ling iin the range of from about 68 C; to '74 C., is separated from a liquid fraction comprising 1-methylcyclopentene and' Ll-methylcyclopentene in admixture with close boiling aliphatic hydrocarbons, such as, for example, a fraction boiling in the range of from about 74 C. to about '77 C. The vapor fraction is recycled from fractionator 24 through line 30 into line I4. Before being introduced into line I4 it may be treated to remove diolens or aromatics. The liquid fraction comprising l-methylcyclopentene and 4-m-ethylcyclopentene is taken from fractionator 24 by means of line 3i and forms the charge to a second and separate isomerizing zone of the process.

The 3-methylcyclopentene-containing fraction flowing throughline 28 will comprise a plurality of open chain olefinic hydrocarbons having six carbon atoms to the molecule boiling at, or close to, the boiling temperature of 3-methylcyclopentene. and therefore inseparable therefrom on a practical scale by such expedients as fractionation.

The 3-methylcyclopentene-containing fraction is passed from line 28 into a heating zone, such as, for example, an externally heated coil 33 positioned in a furnace structure 34. From heating coil 33, the heated S-methylcyclopentene fraction is passed through line 35 into a suitable first isomerizing zone. The first isomerizing zone may comprise a reaction chamber 36.

A hydrocarbon fraction consisting essentially of 3-methylcyclopentene in admixture With close boiling aliphatic hydrocarbons may be introduced into line 28 from an outside source by means of valved line 38.

Within reaction chamber 36, the 3-methylcyclopentene fraction is contacted with an olen isomerization catalyst at olen isomerizing conditions set forth fully below, eifecting the conversion of S-methylcyclopentene to unsaturated cyclic olefins consisting essentially of l-methylcyclopentene, 4-methylcyclopentene and a minor amount of cyclohexene. Under the isomerizing conditions maintained in reactor 36 at least a substantial part of the six carbon atom open chain oleiins are simultaneously converted to isomeric open chain olens boiling below 66 C. Isomerization of the S-methylcyclopentene fraction under these conditions is illustrated by the following example:

Eazample II An oleflnic hydrocarbon fraction having a boiling range of from about 66 C. to about 68 C., separated from a catalytically cracked gasoline by fractionation, and having a 3methylcyclopen tene content of 40% and an open chain Cs olefin content of is contacted with a bauxite catalyst at a temperature of 275 C. and a pressure of 15 pounds absolute. A conversion of 3-methylcyclopentene to l-methylcyclopentene and 4methylcyclopentene of '70%, and of open chain olens to olens boiling below 66 C. of 30% is obtained. Only about 0.5% of the 3-m-ethylcyclopentene is converted to cyclohexene.

Eiiiuence from reactor 36 comprising l-methylcyclopentene, 4methylcyclopentene, unconverted 3-methylcyclopentene, some cyclohexene, and the open chain isomerized and unisomerized six carbon atom olens is passed through line 39, provided with suitable cooling means, such as, for example, a heat exchanger 40, into a product separating zone. Since the highest boiling noncyclic Cs olefin boils at 73 C., and 1methyl cyclopentene, 4-methylcyclopentene and cyclofil) 8 hex-ene boil at C., 76 C. and 83 C., respectively, the 1- and 4methylcyclopentenes along with the cyclohexene are readily separated from the reactor eiiluenc-e by fractionation.

The product separating zone receiving reaction products from line 39 is depicted in the drawing by fractionators 4l and 42. Within fractionator 4l a vapor fraction comprising isomerized open chain olens boiling below 60 C. is separated from a liquid fraction vcomprising 'hydrocarbons boiling above 66 C. The liquid a liquid fraction from a vapor fraction having a boiling range of about 66 C. to about 74 C. comprising unconverted S-methylcyclopentene in 'admixture with close boiling aliphatic oleiins. At

least a part of the vapor fraction is recycled from fractionator 42, through line 45, into line 28. Valved line 46 is provided to enable the bleeding of a portion of the recycle stream from the system to avoid the accumulation of saturated hydrocarbons boiling lin the boiling range of the recycled stream. Although such bleeding will generally suffice, a portion or all of the recycle streain may be by-passed through suitable saturated hydrocarbon-removing means, such as, for example, an extraction zone not shown in the drawing. The liquid fraction comprising 1- and Ll-methylcyclopentene and cyclohexen is taken from fractionator 42 through valved line 48.

Th-e hydrocarbon fraction comprising 1-methylclopentene and 4-methy1cyclopentene separated from the dehydrogenation products, passing through line 3l, will often comprise close boiling heptenes inseparable from these methylcyclopentene isomers by ordinary fractionating means, as Well as some benzene, toluene, and other higher boiling hydrocarbons. The amount of heptenes present will generally be dependent upon the range of the methylcyclopentane fraction passed to the reaction chamber I8. Due to the complexity of composition of the fraction when substantial amounts of such open chain aliphatics are pres-ent, it does not lend itself to treatment for the direct conversion of the methlycyclorpentene content thereof to cyclohexene of high purity on a practical scale. In accordance with the invention when the hydrocarbon stream flowing through, line 3l comprises substantial amounts of open chain aliphatics, it is passed into a heating zone, such as, for example, an externally heated coil 53, positioned in a furnace structure 54. From coil 53 the heated hydrocarbon stream is passed through line 55 to a second isomerizing zone of the process, such as, for eX- ample, a reaction chamber 56.

Additional hydrocarbons from an outside source consisting essentially of 1- and 4-methylcyclopentenes in admixture with close boiling open chain olens having seven carbon atoms to the molecule may be introduced into the system by means of valved line 58.

Within reactor 56 the hydrocarbon stream is contacted with an olefin isomerizing catalyst at olefin ismerizing vconditions effecting the conversion of 1-methy1cyc1opentene and 4-methylcyclopentene to cyclic olens consisting essentially of S-methylcyclopentene and some cyclohexene.

Eflluence from reactor 56 is passed through line 60, provided with suitable cooling means such as. for example, a heat exchanger 6|, into a product separating zone. The product separating z one reg of the solid type. Suitable olefin isomerizing catalysts comprise, for example, the naturally occurring or synthetically prepared solid adsorptive aluminous materials, such as the aluminum oxides, activated alumina, bauxite, silica-alumina, etc. These catalytic materialsmay be subjected to a pretreatment before use. Such pretreatments comprise, for example, subjection to elevated temperatures, optionally in the presence of gaseous materials such as hydrogen, nitrogen, steam, gases comprising them or the catalysts may be contacted with an inorganic mineral acid such as hydrochloric acid, sulfuric acid, carbamic acid, hydrofluoric acid, boric acid, etc. A particularly preferred type of catalyst comprises adsorptive aluminous materials containing substantial amounts of gamma alumina which has been pretreated with an acidic material. Although adsorptive materials are preferred as catalysts for the isomer-ization of the methylcyclopentenes, the invention is not necessarily limited thereto and other catalysts capable of activating the olefin isomerization reaction may be employed. Such catalysts comprise, for example, catalysts of the type of naturally occurring siliceous materials such as clays, bentonites, or the like, alumina-silica compounds or mixtures thereof, zeolites, oxides of Be, Si, Ti, Th, V, Zr, Mn, etc. Other suitable catalysts are those comprising phosphoric acid and silica, as well as any acid of low voltaility, preferably on a solid oxide support material. Of the isomerization catalysts, those consisting essentially of alumina in combination with silica are somewhat preferred.

Temperatures within reactors 36, 56 and 18 are maintained in the range of from about 150 C. t0 about 650 C., and preferably from about 200 C. to 550 C. Temperature conditions in reactors 36, 56 and 18 are controlled by the heat input into the hydrocarbon streams flowing through externally heated coils 33, 53 and 15, respectively. tThe isomerization reactions are preferably executed in the Vapor phase. Atmospheric or superatmospheric presures may be maintained within reactors 33, 53 and 15. Pressures close to atmospheric have been found satisfactory. Throughput rates in terms of a liquid hourly space velocity in the range of, for example, from about 0.5 to about 25 are employed.

Although substantially identical conditions of temperature and throughput rate ranges as well as the same types of catalyst may be employed in all three of the olefin isomerizing zones of the process, within the scope of the invention, in a preferred modification milder olefin isomerizing conditions are maintained in reaction chambers 36 and 56 than in reaction chamber 18. Thus, in the modication of the invention, an isomerization catalyst selected from the group consisting of silica-phosphoric acid type catalysts, activated alumina, or bauxiteis employed in reaction chambers 36 and 56, While a catalyst such as, for eX- ample, a catalyst consisting essentially of acidtreated adsorptive alumina, or alumina in combination with silica, is employed in reaction chamber 18. Milder isomerization conditions within reaction chambers 36 and 56 may also be obtained by maintaining therein temperatures within the lower range of the prescribed suitable s operating range, such as, for example, a temperature in the range of from about 150 C. to about 350 C., While the higher temperatures in the prescribed broad temperature range, such as, for example, a temperature of from about 400 C. t0

about 550 C., are maintained within reaction f chamber 18.

Under the above-defined conditions S-methylcyclopentene is converted to cyclic oleflns consisting ypredominantly of 1- and 4-methylcyclopentenes in reactor 36; 1- and 4-methylcyclopentenes are converted to cyclic olens consisting essentially of S-methylcyclopentene in reactor 56 invention comprising, for example, pumps, condensers, complete fractionating systems, accumulators, etc., have been omitted from the drawing. It is to be understood that the apparatus shown may be modified as apparent to one skilled in the art without departing from the scope of the invention.

The claimed invention is:

1. The process for the production of cyclohexene in a relatively high state of purity from a hydrocarbon fraction consisting essentially of methylcyclopentane in admixture with close boiling open chain hydrocarbons, which comprises contacting said methylcyclopentane fraction with a dehydrogenating catalyst under dehydrogenating conditions converting methylcyclopentane to methylcyclopentene in a dehydrogenating Zone, fractionating from the eiiluence of the dehydrogenating zone a lower boiling fraction comprising 3methylcyclopentene in admixture with close boiling open chain hydrocarbons and a higher boiling fraction comprising 1methylcyclopentene and 4-methylcyclopentene in admixture with close boiling open chain hydrocarbons, contacting said lower boiling fraction with a solid adsorptive aluminous material under isomerizing conditions effecting the conversion of 3methylcyclopentene to l-methylcyclopentene and 4-methylcyclopentene in a iirst isomerizing zone, fractionating l-methylcyclopentene and Ll-methylcyclopentene free of any substantial amount of open chain hydrocarbons from the eflluence of the rst isomerizing zone, contacting said higher boiling fraction with a solid adsorptive aluminous material under isomerizing conditions effecting the conversion of l-methylcyclopentene and 4-methylcyclopentene to S-methylcyclopentene in a second isomerizing zone, fractionating 3-methylcyclopentene free of any substantial amount of open chain hydrocarbons from the eflluence of the second isomerizing zone, contacting said l-methylcyclopentene and Ll-methylcyclopentene separated from the efluence of said first isomerizing Zone together with the 3-methylcyclopentene separated from the eiiiuence of the second isomerizing zone with a solid adsorptive aluminous material under isomerizing conditions effecting the conversion of methylcyclopentenes to cyclohexene in a third isomerizing zone, and fractionating cyclohexene in a high state of purity from the eflluence of said third isomerizing zone.

2. The process for the production of cyclohexene in a relatively high state of purity from a hydrocarbon fraction consisting essentially of methylcyclopentane in admixture with close boiling open chain aliphatic hydrocarbons, which comprises contacting said methylcyclopentane fraction with a dehydrogenating catalyst under dehydrogenating conditions converting methylcyclopentane to methylcyclopentenes in a dehydrogenating zone, fractionating from the effluence of the dehydrogenating zone a lower boiling fraction comprising 3-methylcyclopentene in admixture with close boiling open chainhydrocarbons and` a higher boiling fraction comprising. 1.-methylcyclopentene and 4-methylcyclopentenef inadmixture with close boiling open chain hydro,- carbons, contacting said lower boiling fraction with a catalyst consisting essentially of adsorptive alumina. under isomerizing conditions effecting1 the conversion of S-methylcyclopentene to 1 methylcyclopentene and 4-methylcyclopentene in a rst isomerizing Zone, iractionating l-methylcyclopentene and Ll-methylcyclopentene free of any substantial amount of open chain hydrocarbons, from the eiiluence of the iirst isomerizing zoneL contacting said higher boiling fraction with a, catalyst consisting essentially of adsorptive alumina under isomerizing conditions effecting` the conversion of l-methylcyclopentenc and 4-methylcyclopentene to S-rnethylcyclopentene in a second isomerizing zone, f ractionating S-methylcyclopentene free of any substantial amount of open chai-n hydrocarbons from the eliluence of the second isomerizing zone, contacting said 1- methylcyclopentene and Ll-rnethylcyclopentene separated from the eliluence of said first isomeriz.- ing zone together with the S-methylcyclopentene separated from the e-fluence of the second isozoney with a catalyst consisting essenally of adsorptive alumina in combination with silica under isomerizing conditions effecting the conversion of methylcyclopentenes to cyclohexene in a third isomerizing zone, and fractionating cyclohexene in a high state of purity from the eluence of said third isomerizing Zone.

3,. The process for the production of cyclohexene in a relatively high state of purity from a hydrocarbon fraction consisting essentially of methylcyclopentene in admixture with close boiling open chain aliphatic hydrocarbons, which` comprises contacting said rnethylcyclopentane raction with a dehydrogenating catalyst under dehydrogenating conditions converting methylcyclopentane to methylcyclopentenes in a dehydrogenating zone, fractionating from the ef-y uence of the dehydrogenating zone a lower boil-- ing fraction comprising 3--methylcyclopentene in admixture with close boiling open chain hydro,- carbons and a higher boiling fraction comprising l-methylcyclopentene and -methylcyclopentene in admixture With close boiling open chain hydrocarbons, contacting said lower boiling fraction with a solid olefin isomerizing catalyst under isomerizing conditions effecting the conversion of S-methylcyclopentene to l-methylcyclopentene and l-methylcyclopentene in a rst isomerizing zone, fractionating l-methylcyclopentene and 4- methylcyclopentene free of any substantial amount of open chain hydrocarbons from the effluence of the rst isomerizing zone, contacting said higher boiling fraction with a solid olenisomerizing catalyst under isomerizing conditions eiecting the conversion of 1rnethylcyclopentene and lmethylcyclopentene to B-methyleyclopentene in a second isomerizing zone, fractionating 3-methylcyclopentene free of any substantial amount of open chain hydrocarbons from the ellluence of the second isomerizing zone, contacting said 1-methylcyclopentene and 4- methcyclopentene separated from the eflluence of said first isomerizing zone together with the 3- methylcyclopentene separated from the ellluence of the second isomerizing zone Iwith a solid olefin isomerizing catalyst under isomerizing conditions effecting the conversion of methylcyclopentenes to cyclohexene in a third isomerizing zone, and fractionating cyclohexene in a high state of pur- 1.4 ity from.. the eiucnce of said third isomerizing. zione.y

4.. The process for the production of cyclohexene in a, relatively high State of; pur-ity from cracked gasoline. comprising; methylcyclopentane in admixture with close boiling open chain alfiphatic, hydrocarbons,A which comprises fractionating a, methylcyclopentane frac-tion boil-ing in the range: of; from` about. 6.8. C. to about 74 C'. from said. gasoline, contacting said methycyclopentane fraction. with a dehydrogenating catalyst under dehydrogenating conditions converting methylcyclopentane to methylcyclopentenes. in a dehydrogenating zone,4 tractionati-ng from the eluence of the dehydrogenating Zone. a lower boiling frac-tion boiling in the range of from about 66o C. t0, about 686' comprising S-methylcycloponton-e. in admixture. with close boiling open chain hydrocarbons and a higher boiling fraction having a boiling range of from about 74 C. to about 71 O. comprising l-methylcyclopentene and 4-methylcyclopentene in admixtnre with close boiling open, chain hydrocarbons, contacting said. lower boiling fraction with a solid oleinv isomerizing catalyst under isomerizing conditions effecting; the conversion of S-methycyclopentene to l-meth-ylcyclopentene and 4-methylcyclopentene, in a first.v isomerizing zone,y fra-otionating lmethyoyolopentene and l-methylcyclopentene free of any substantial amount of open chain hydrocarbons from the emu-ence of the rst isonicriz'ing zone, contacting said higher boiling fraction with a solid olefin isomerizing catalystv under somerizing conditions. effecting the cony version o' l-methyloyelopentene and 4-methylcyolopentene to r-methylcyclopentene in a second isomerizing zone, fractionating S-methylcyclopentene free of any substantial amount of open chain hydrocarbons from the ellluence of the second isomerizing zone, contacting said 1- metliylcyclopentene and 4methylcyclopentene separated from the eilluencel of said rst isomer-izing Zone together with the 3-methylcyolopentene separated from the eluence of the second isomerizing zone with a solid olen isomerizing catalyst under isomerizing conditions eiecting the conversion of meth-ylcyclopentenes to cyclohexane in a third isomerizing zone, and fractionating cyclohexene in a high state of purity from the eflluence of said third isomerizing Zone.

5. The Process for the production of cyclohexene in a high state of purity from a hydrocarbon fraction consisting essentially of methylcyclopentane in admixture with close boiling open chain aliphatic hydrocarbons, which comprises contacting said methylcyclopentane fraction with a dehydrogenatng catalyst under dehydrogenating conditions converting methylcyclopcntane to methylcyolopentenes in a dehydrogenating zone, fraetionating from the elluence of the dehydrogenating zone a fraction comprising 3-methylcyclopentene in admixture with close boiling open chain hydrocarbons, contacting said S-methylcyclopentene fraction with a solid aluminous material under isomerizing conditions effecting the conversion of S-methylcyclopentene to l-methylcyclopentene and l-methylcyclopentene in a first isomerizing zone, fractionating methylcyclopentenes consisting essentially of l-methylcyclopentene and Ll-metliylcyclopentene free of any substantial amount of open chain aliphatic hydrocarbons from the elluence of said first isomerizing zone, contacting said methylcyclopentenes fractionated from the eliiuence of said rst isomerizina zone with. a solid aluminous. material ll under isomerizing conditions effecting the conversion of methylcyclopentenes to cyclohexene in a second isomerizing zone, and iractionating cyclohexene in a relatively high state of purity from the effluence of said second isomerizing zone.

6. The process for the production of cyclohexene in a high state of purity from a cracked gasoline fraction consisting essentially of methylcyclopentane in admixture With close boiling open chain aliphatic hydrocarbons, which comprises contacting said methylcyclopentane fraction With a dehydrogenating catalyst under dehydrogenating conditions converting methylcyclopentane to methylcyclopentenes in a dehydrogenating Zone, fractionating from the eliiuence of the dehydrogenating zone a fraction comprising -methylcyclopentene in admixture with close boiling open chain hydrocarbons, contacting said 3-methylcyclopentene fraction with a catalyst consisting essentially of adsorptive alumina under isomerizing conditions effecting the conversion of 3- methylcyclopentene to l-methylcyclopentene and 4-methylcyclopentene in a rst isomerizing Zone,

ractionating methylcyclopentenes consisting essentially of l-methylcyclopentene and li-methylcyclopentene free of any substantial amount of open chain hydrocarbons from the eiiluence of said first isomerizing zone, contacting said methylcyclopentenes fractionated from the effluence of said rst isomerizing zone with a catalyst consisting essentially of alumina in combination with silica under isomerizing conditions effecting the conversion of methylcyclopentenes to cycloheXene in a second isomerizing zone, and separating cyclohexene in a relatively high state of purity from the eflluence of said second isomerizing zone.

7. The process for the production of cycloheXene in a high state of purity from a hydrocarbon fraction consisting essentially of methylcyclopentane in admixture with close boiling open chain aliphatic hydrocarbons, which comprises contacting said methylcyclopentane fraction With a dehydrogenating catalyst under dehydrogenating conditions converting methylcyclopentane to methylcyclopentenes in a dehydrogenating zone, fractionating from the eiiiuence of the dehydrogenating zone a fraction comprising S-methylcyclopentene in admixture With close boiling open chain aliphatic hydrocarbons7 contacting said S-methylcyclopentenecontaining fraction with a solid olefin isomeriZ- ing catalyst under isomerizing conditions effecting the conversion of 3-methylcyclopentene to 1- methylcyclopentene and 4methylcyclopentene in a irst isomerizing zone, fractionating methylcyclopentenes consisting essentially of l-inethylcyclopentene and l-methylcyclopentene free of any substantial amount of open chain aliphatic hydrocarbons from the efuence of said first isomerizing zone, contacting said methylcyclopentenes fractionated from the eluence of said first isomerizing zone with a solid olefin isomerizing catalyst under isomerizing conditions eiecting the conversion of methylcyclopentenes to cyclohexene in a second isomerizing Zone, and separating cyclohexene in a relatively high state of purity from the eflluence of said second isomerizing zone.

8. The process for the production of cyclohexene in a high state of purity from a hydrocarbon fraction consisting essentially of methylcyclopentane in admixture with close boiling open chain aliphatic hydrocarbons, Which comprises contacting said methylcyclopentane fraction with a dehydrogenating catalyst under dehydrogenating conditions converting methylcyclopentane to methylcyclopentenes in a dehydrogenating Zone,

fractionating from the eilluence of the dehydro genating zone a fraction comprising l-methylcyclopentene and 4-methylcyclopentene in admixture With close boiling open chain hydrocarbons, contacting said 1- and i-methylcyclopentene fraction With a catalyst consisting essentially of adsorptive alumina under isomerizingconditions eiecting the conversion of l-methylcyclopentene and Ll-methylcyclopentene to 3- Inethylcyclopentene in a rst isomerizing zone, fractionating S-methylcyclopentene free of any substantial amount of open chain aliphatic hydrocarbons from the effluence of said first isomerizing zone, contacting said S-methylcyclopentene separated from the eiliuence of said rst' isomerizing zone with a catalyst consisting essentially of adsorptive alumina under isomerizing conditions effecting the conversion of methylcy clopentenes to cyclohexene in a second isomerizylcyclopentane in admixture with close boiling' open chain aliphatic hydrocarbons, Which comprises contacting said methylcyclopentane fraction with a dehydrogenating catalyst under dehydrogenating conditions converting methylcyclopentane to methylcyclopentenes in a dehydrogenating zone, iractionating from the eluence of the dehydrogenating Zone a fraction comprising l-methylcyclopentene and 4-methylcyclopentene in admixture With close boiling open chain hydrocarbons, contacting said 1- and 4-methy1cyclopentene fraction With a catalyst consisting essentially of adsorptive alumina under isomerizing conditions eiecting the conversion of l-methylcyclopentene and 4-methylcyc1opentene to 3- methylcyclopentene in a rst isomerizing zone, fractionating 3-methy1cyclopentene free of any substantial amount of open chain aliphatic hydrocarbons from the ellluence of said first isomerizing zone, contacting said 3-methylcyclopentene separated from the eluence of said first isomerizing zone With a catalyst consisting essentially 0f alumina in combination with silica under isomerizing conditions effecting the conversion of methylcyclopentenes to cyclohexene in a second isomerizing zone, and separating cyclohexene in a relatively high state of purity from the effluence of said second isomerizing zone.

10. The process for the production of cyclohexene in a high state of purity from a hydrocarbon fraction consisting essentially of methylcyclopentane in admixture with close boiling open chain aliphatic hydrocarbons, which comprises contacting said methylcycl-opentane fraction with a dehydrogenating catalyst under .dehydrogenating conditions converting methylcyclopentane to methylcyclopentenes in a dehydrogenating zone, fractionating from the eiiluence of the dehydrogenating zone a fraction comprising l-methylcyclopentene and 4-methylcyclopentene in admixture With close boiling open chain hydrocarbons, contacting said 1- and l-methylcyclopentene fraction with a solid olefin isomerizing catalyst under isomerizing conditions effecting the conversion of l-methylcyclopentene and 4-methy1cyclopentene to B-methylcyclopenetene in a lrst isomerizing zone, fractionating 3-methy1cyc1opentene free of any substantial amount of open REFERENCES CITED chain aliphatic hydrocarbons from the efuence of said rst somerizng zone, contacting said 3- lrhf ggwleerens are of record m the methylcyclopentene separated from the affluence p of said rst isomerizing zone with a solid olen 5 UNITED STATES PATENTS isomerizing catalyst under isomerizing conditions effecting the conversion of methylcyclopentenes Number Name Date to oyclohexene in a second isomerizing Zone and 2265583 stevens et al' Dec' 9 1941 2,385,555 Voge et al. Sept. 25, 1945 separating cyolohexene in a relatively high state of purity from the efuence of said second isolo merzing Zone.

HERVEY H. VOGE. GEORGE M. GOOD. 

